This invention relates in general to submersible pumps, and in particular to an electrical coupling that provides a boundary between high and low pressure zones and also provides an electrical connection between electrical cables in the low and high pressure zones.
In a typical large volume submersible pump installation, an electrical motor will be located downhole for rotating a centrifugal pump. Electrical conductors extend from the surface to the motor. If the wellhead is under pressure, the conductors must feed through a barrier separating high wellhead pressure from low surface pressure. Also, in certain installations using downhole packers, the conductor must extend from a high pressure zone into a low pressure zone.
Feed-through mandrels are available for providing a barrier between different pressure zones and for connecting electrical cable from the two separate zones. These mandrels usually have a thermoset insulation material molded around copper conductors. In general, these types will withstand up to about 3,000 psi (pounds per square inch) pressure differential. One disadvantage is that if gas is present in the wellhead, the gas may enter the thermoset material under pressure. When pressure is relieved, the gas will expand, possibly destroying the insulation material.
It is known that glass based materials, such as glass bonded mica, can be compressed against a rigid surface such as metal to very high pressures to form a seal. Also, these glass bonded mica materials are dielectric, thus provide good insulators. Feed-through mandrels for submersible pump installations, to applicant's knowledge, however, do not utilize glass based materials.